This invention relates to mechanical vacuum pumps and, more particularly, to an improved system for lubricating the pump's internal moving parts.
Rotary, oil-sealed mechanical vacuum pumps have used the oil bath surrounding the pumping mechanism both to seal gaps between parts and to lubricate various bearing and wear surfaces. In one typical arrangement, the lubrication has been accomplished by introducing oil into the pumping mechanism by leakage through the annular gap between the pump shaft and the bearing within which it rotates, or between the small rotor-to-stator gap or rotor-to-end plate gap. Examples of these lubrication systems can be found in U.S. Pat. Nos. 3,525,578; 3,040,573; 2,877,946; and 2,337,849. Drawbacks common to each of these systems are: no provision for the accurate metering of the amount of oil introduced into the pumping mechanism and no provision for interrupting the admission of oil to the pumping mechanism when the pump is not operating.
Other prior lubricating systems have involved the use of external valve arrangements, with the valves being operated by cams driven by the rotation of the shaft. These systems, of course, are more complex, more expensive, and provide a greater inherent likelihood of mechanical failure.
In view of the foregoing, the principal object of the present invention is to provide a lubrication system for a mechanical vacuum pump that is positive in operation and that delivers a precisely metered amount of lubricant to the pumping mechanism. Further objects are to provide such a lubrication system that is inexpensive to manufacture, that is substantially maintenance-free, and that acts to interrupt the flow of lubricant when the pump is not operating.